When did the Amtrak route structure reach its greatest number of route miles?

In the 70s (pre-Carter cuts)?

In the 80s?

In the 90s?

Time to pull out your timetables and check!

Without looking at actual numbers, I'd guess in the 70s just before the Carter cuts or in the 90s just after the SUNSET LIMITED was extended to Florida (and the PIONEER and DESERT WIND were still running).